Needing some suspension set up advice... Update (3) in original post

bmarshall1

Posted 07-23-2015 07:24 AM

bmarshall1

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Car Year:1999

Car Number:23

Hello All you suspension Gurus,

UPDATE (1) 7/24 - Left Front alignment nut side cams had the little nubs worn off and were not rotating with the alignment bolt leading to inconsistent readings, I replaced the nut side cams and all seems well, I am working on the right side front now and think I may have a bent upper control arm (the bolt is bent by about 1 mm). I am going to compare the upper arm and spindle to my spares. How common is it to bend the lower? I have lower control arm spares as well but not sure the spare is good.

UPDATE (2) 7/25 - Confirmed bent RF upper control arm, slightly bent upper control arm bolt, spindle seems to be OK; the bearings roll free and measurements and angles match my spare. I will now be checking the lower A arm.

UPDATE (3) 7/26 - Lower 'A' arms OK, I don't have jigs, but do have several spares and anything that did not match the others was considered bent, I also did a 'mirror' comparison of left to right pieces and Dave's 'feel test' from another thread. Both subframes are checked and match my spares. I also found a lengthy thread where Dave and Keith (and others) were helping Flyintgr and found a lot of good info there. As well I also realized there is a Version 2 of Jim's suspension set up.

Proposed set up (or as close as I can get to it), is this a good novice, general set-up?:

Front

toe - total toe out 1/8 as measured at 21" on the toe plate

Camber 3.0Â°

Caster 4.5Â°

Rear

toe - total toe in 1/16 as measured at 21" on the toe plate

Camber 2.5Â°

Fatcats and offset bushings will be installed over the winter, but I am on a mission to learn how to set up in it's current state prior to 8/5 hip surgery.

>>>What have I overlooked or what are your suggestions at this point?

***You have all been very helpful, I cannot imagine any other sport where your competitors are so willing to help!

After being hit in my last race I am using this opportunity to give my suspension a thorough once over. It's a '99 SM, I have the car on scales at 50%, front shock travel is 5/8 front and rear is 3/4. No Fatcat mounts. Experience wise, I am a novice.

I have Dave's book and used it, I have read Jim's upload as well and used that to get the car 'square' at 2.8Â°. I have a few Q's about set up and am looking for good base line numbers.

I have replaced any bent parts with know good ones, here's my dilemma and questions...

>> The most camber in the rear I can get equally is about 2.8Â°, the least camber I can get in the front equally is 2.8Â°, this is all at 0 toe. RF caster is 8.5 Â°, and LF caster is 5.5Â°. (I maxed the RF caster to get to 2.8Â°). The numbers are correct, my neighbor is an ex NASCAR crew chief and he assisted. Jim's upload says go for 2Â° on all corners, other conventional wisdom says give the front +.5Â° of camber over the rear. At the track I see many Miata with a lot more than 2Â° camber all around and more camber in front than rear.

Given these numbers, can anyone recommend a course of action to set up my car. I was thinking 2.7Â° rear w/ 1/16 toe in per side, and front at 3.2Â° camber w/ 1/16 toe out per side and 4.5Â°caster and leave the ride height as-is. Rear sway set to full soft.

or.. do I max out camber and call it good?

Another option is to install a spare set of front spindles or get the offset bushings to reduce front (or increase rear camber) but I would rather not if it is not needed.

I just need a good baseline setting so I can improve myself and get back to a neutral setting if needed. I doubt I will be making on-track adjustments.

davew

Posted 07-23-2015 08:10 AM

davew

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You still have something bent. With everything straight, w/o offset bushings you should be in the range of: -2.8 camber front, -3.5 camber rear, +3.5 caster front and basicly zero toe all around. If you can not get those numbers you have bent components. No ifs, ands, or buts, something is bent.

Please clarify this statement <<The most camber in the rear I can get equally is about 2.8Â°, the least camber I can get in the front equally is 2.8>>

Does this mean the most NEGATIVE rear camber you can get is 2.8*? You say "equally". Does that mean one side will get more? Do you mean the LEAST NEGATIVE camber you can get is 2.8*?

chris haldeman

Posted 07-23-2015 09:57 AM

chris haldeman

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Any of us will help you arrive at a good baseline set up. Even more true any of our baselines will be very close too each other. Take this opportunity while the set up is whack too install fat. Cats before continuing with set up. Dave at advanced stocks them and they are cheap in the world of racing. Also add the now allowed offset front upper bushings too. Do it once right and your life will be much easier.

Keith Novak

Posted 07-23-2015 10:09 AM

Keith Novak

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I agree with Dave. Not getting less than 2.8* negative camber in front sounds very very odd. I've had lots of issues with not being able to get more than that in front but not being able to get less makes me think all is not right in Denmark.

davew

Posted 07-23-2015 10:18 AM

The offset bushings are only for the front and only are to give you more negative camber.

You should also get a set of my subframe checkers. They will very quickly tell you if the lower mounts on the subframe are bent.

What parts did you replace? and how was the car hit? How did you determine that the replacement parts where "known good"? I have seen many used parts, that looked fine, actually be bent when checked in the jigs.

The more info the better. Off to Road America after lunch. I am sure someone else will pipe in with advise.

Mark

Posted 07-23-2015 11:01 AM

Mark

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On the front of the miata everything affects everything else. Adjusting is an iterative process as a result. Camber changes affect toe and caster, adjusting caster changes camber and toe, etc. Get all adjustments close before measuring. Think rubics cube. It is similar. To get close - In the front, assuming nothing is bent for an NB we start with the rear cam bolts eccentrics straight up. Max out the camber with the front cam bolts (eccentric pointed in), set toe to zero to slightly out. This usually nets something around +5-6 caster and 2.8-3.2 neg camber at a 4 5/8 seam weld height. When setting ride height make sure to have the car on slip plates or roll it after every change to settle the suspension. Rear is easier. NP getting to -3.5-4 camber unless something is bent. Ride height dictates camber though. If you are setting up at a 5 1/4 seam weld height you won't get the camber numbers you want. Do yourself a favor though before going through all the pain to set up the car and get the fat cats and offset camber bushings installed first.

Posted 07-23-2015 01:12 PM

Johnny - Thanks for the offer of help but this weekend was not my best. Unfortunately I spun in turn 7 during qualifying and got hit on both front and rear right side corners. This bent a tie rod, a rear suspension lower A arm bolt, a broken motor mount plus body damage (both cars that hit me suffered broken differential housings) With help from SpeedWorksRacing we got it all put back together but could not get the rear under 1/2" toe out, but everything looked straight otherwise. Russ McBride and myself got under the car later and we diagnosed a possible bent rear sub frame. That night my wife and I slept in the trailer and it was a little cold and windy to say the least. The wind ended up destroying our pop up canopy and scratched up the hood of my race car pretty good, how it got loose but did not tear up my trailer I do not know. Then the next morning there was no hot water in the showers... my normally lovely and understanding wife was cold, bored, tired, grumpy, had no coffee. She was also about out of patience and did not want me driving a car that was not 100% sorted. Myself I was tired and have a bad hip that was hurting after a day of wrenching on the car on the cold asphalt.

On the way out I stopped by and talked to Steve at Panic Racing to source parts and in his experience it was most likely a bent upright or upper control arm, which he kindly sold me his spares. But by that time both Jen and I were ready to go so we did. After the windy and white knuckle drive home I am now sitting on my couch eating pizza and reading about what I missed. we were able to watch a little bit of today's race just prior to leaving and it was awesome and hard fought, my hats of all the participants. Now is my time to step back, fix the car and prep for next year - hip surgery in December and I'll see you all next season! I want to thank everyone for their help and getting as far along as I have.

bmarshall1

Posted 07-23-2015 01:22 PM

bmarshall1

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Car Number:23

Thanks for all the good replies/questions, I'll answer as best I can

The RF was hit on the leading edge of the tire, hard enough to bend the tie rod, the rear was hit on the trailing edge of the tire, hard enough to bend the hub and upper A arm. I had several sets of F and R arms so I compared and the bent one was obvious, since the rest were essentially the same I *assumed* they were good to go. I replaced all rear components, and the front tie rod. The car is sitting on slip plates on scales.

Ride height at pinch welds is about 4 5/8 in front, 4 15/16 rear, so about 5/16 rake (slightly more than 1/4)

Clearance measured at the shock bump stop, front 5/8, rear is 3/4

No Fatcats (yet), I am between jobs at the moment and would have a hard time justifying this to the wife! (but I also understand do it right - once)

I bought the car used, so is it possible it has 'tweaked' front uprights for more camber? (I have what I feel is a straight set I can put them on for comparison)

Here are the max Camber Settings I was able to get at 0Â° toe

left right

Front -4.8 -5.5

Rear -2.7 -3.2

What are the camber numbers I am looking to achieve F and R?

If the front uprights are bent, does it not achieve the same end goal as offset bushings, would it be OK to run these uprights or is that a big No No? I want to remain legal above all else (nobody has to worry about me being on the podium at this time .

Dave - I will be putting in an order, but it does not seem at this point offset bushing would help me s I have plenty of front camber, correct?

If I pony up for the Fatcats,do I still measure by the distance to the bumpstop, or is the pinch weld the place to determine ride height?

thanks everyone for your assistance, let me know what other information I can provide to help you help me.

Keith Novak

Posted 07-23-2015 03:19 PM

Keith Novak

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Front at -4.8 and -5.5 without eccentric bushings sounds mucho bent. The rear doesn't sound too bad. I'll take a few measurements of my straight '99 when I get home between the top of the shock towers and between the cam adjusters for comparison. I don't know if the measurement at the top of the shocks will compare though w/o Fat Cats

bmarshall1

Posted 07-24-2015 11:05 AM

This is what I am fixing at this time, unfortunately the car has sat since last fall. Hip surgery was delayed and life got int the way... I am between jobs right now and have all the time needed to devote to the car.

Hip surgery is coming Aug 5th and baby coming early Nov. My goal is to have a sorted car before Aug 5th so I can make some races in spring of 2016

bmarshall1

Posted 07-25-2015 05:27 AM

Ok then. It took me a while to figure out how to put pictures in this but here we go.

To measure the cams, I had to make a very low tech version of Dave's tool:

Very complex stuff. Measuring the outside edge of the cam slots on 4 subframes (2 NA and 2 NB) I found the distance between outside edges is 27 1/8 (and one bent spare that goes in the trash).

Then I made a very high tech tool to measure the centerlines of the two top bolts on the shocks as so:

And found they are 37 15/16 apart measuring between the clamps.

Keith - I went to Harbor Freight and they had 24" long reach calipers, I was able to remove the travel stop screw and that allows it to measure to 27", clearance price $11.99 . I measured all my subframes at 27 1/8 (or 690 mm). My shock measurements were the same as yours also. Therefore subframe is OK, in my original post I discovered bent parts and bad alignment cams.